The invention is directed generally to a scale testing cart adapted to transport calibrated weights for the calibration of high capacity performance scales and more specifically to a means for balancing the scale cart as it is lifted and transported from the bed of a larger weight transportation vehicle onto the platform scales, and further; a means for substantially fine tuning the combined weight of the scale testing cart and calibration weights carried by the cart to a predetermined weight.
Platform scales are well known and are utilized for many purposes. For example, platform scales are utilized by commercial enterprises which deal in large quantities of bulk materials, such as grain elevators. Similarly, government regulations create a demand for the use of platform scales to determine whether semi-tractor and trailer units are in compliance with the highway load limits delineated by state vehicle weight limit enforcement programs. Common weight loads for platform scales generally range from 20 tons to 100 tons.
Platform scales are often designed to combine a plurality of individual platforms by mechanical linkage or by electronic load cells. As a vehicle rests on one or more of the platforms, its weight will be accurately transmitted to the indicator through the mechanical linkage or electronic load.
Because of the applications in which platform scales are used, dirt and friction have a tendency to build up at critical points in the linkages, thereby restricting the action of the mechanisms. When this occurs, the scales do not indicate a weight which corresponds to the actual weight of the load. Similarly, drift in the components of electronic scales will effect their calibration, causing the reading to not correspond with the proper weight. In either event, overpayment or underpayment for a load of bulk material or mistakes in weighing a properly loaded vehicle are manifest.
It is important to periodically calibrate platform scales in order to counter the difficulties described above. In the past, platform scales have been tested by placing individual weight units, normally 500 pound units or 1000 pound units, upon the individual platform sections of a scale. Obviously, this method requires a considerable amount of time and manpower to unload the weights, test the scales and reload the weights onto the weight transporting vehicle.
In addition to the recognized need for calibration, it is also known that the accuracy of platform scales will vary at different loadings. That is, scales may indicate the correct weight at one point in their range but exhibit a deviation from the correct indication at another point of their range. Therefore, calibration techniques required by state agencies commonly require platform scales to be calibrated at different loadings, the heaviest loading often being substantially above the scales' rated capacity.
Furthermore, it has been found that the particular placement of a vehicle on a scale platform also effects the indication of the scales. Approved calibration techniques therefor also require that the scales be calibrated with the weights positioned at various locations upon the scale platform. The constraint of time and the necessity of varying the amount and location of weight on a scale to insure proper calibration suggests that a device which is easily transportable, which is capable of carrying a substantial quantity of calibration weights, which uniformly distributes the weight it is carrying and which is easily moveable about a platform scale is desirable.
One solution involves a vehicle which carries a selected quantity, up to eighteen thousand pounds, of calibration weights. The vehicle is small enough to be carried to the platform scale undergoing calibration on the bed of the weight transportation vehicle, and is also capable of being maneuvered about a platform scale to various desired locations.